Well perforating method and means therefor



May 1, 1962 J. D. cHEsNUT WELL PERFORATING METHOD AND MEANS THEREF OR Filed Aug. 22, 1955 INVENTOR JOHN D. cHEs`NUT May 1, 1962 J, D. CHESNUT 3,031,964

WELL PERFORATING METHOD AND MEANS THEREFOR Filed Aug. 22, 19554 5 Sheets-Sheet 5 INVENTOR.

JOHN D. CHESNUT Unite AStates This invention relates to perforation of wells or well casings.

Wells and well casings are generally perforated by explosive means either by firing armor-jacketed bullets into or through them, or by directing jet blasts from shaped charges at them. If liquids are standing inthe region through which the bullet or jet is to pass, the eifectiv'ei lnessv of theseperforating means is drastically reduced because of the great pressure usually acting on the liquid and the energy consumed in forcing the projectile or jet through it. It is an object of this invention to increase the penetration of such perforating means by displacing liquids from their path so that they need pass only through a gaseous medium. The invention is applicable also to the perforation of wells which do not contain casings,

vand also tothat form of casing perforation known as cas-` ing severing.

In accordance with the present invention, I provide a `method and means for lling the region of the well which is to be perforated with avvolume of gas under suicient pressure to displace any well liquid which may be present and retain the gas as an envelope surrounding the perforating tool so that the per-fora-tng operation can be y performed in this gaseous medium instead of in a liquid medium. Y

A `feature of the invention resides in the provision of a carrier kadapted to be lowered into a well casing, the carrier being provided withperforating means of the explosive type and a gasproducing material. A suitable barrier to yieldably close the casing at the carrier is ernployed. Suitable means initiates the gas production so that gas is formed under pressure and caused to enter the casing below the perforating means and below the barrier.

The perforating mechanism is located somewhat below the barrier and in the region of the casing to be filled with the gas. The release of the gas beneath the barrier will displace all wellliquids upwardly out of the gas filled region so that the perforating means such as bullets or jets will operate in the gaseous medium.

A preferred feature is the use of a gasJproducing charge of -a material which carries the oxygen' for its own combustion'so that outside oxygen such as 4from the atmosphere is not required for producing the gas.

These and other features of the invention vwill be fully understood from the following detailed description and the accompanying drawings, of which:

FIG. l is an elevation,` partly in cross-section, of an embodiment ofy a well perforator incorporating the present invention;` v

FIG. 2 is a cross-section takenat line 2--2 of FIG. 1; FIG. 3 is across-section taken'atlineV 34-3 of FIG. l; FIGS. 4-6 are elevations, partly in cross-section, `of

' other types ofperforatorsincorporating the' invention;

and Y FIGS. 7 and 8 are elevations, partly in cross-section, of still other embodiments of the present invention.

Referring now to the drawings, FIG. 1 shows a jettype perforator incorporating the gas enveloping means of the invention. A carrier 10 is made of a material dense enough to sink in the well. It is suspended in the well casing 11 by an insulated electric line 12. A wire arent 3,031,964 Patented May l, 1962 line socket 12a on the carrier provides an attachment for the line. An access port having a central bore 13 is formed in the top of the carrier and extends downward therefrom. Two or more horizontal perforator ports 14 branch olf from this bore 13, and are plugged olf at the carrier surface by frangible conical retainers 15. The central bore 13 is closed by the socket 12a which is threaded therein as indicated at 16.

The electric line 12 passes through plug 16 and the leads 17 connect to a low resistance detonator I18 within the central bore 13. These leads make contact with a `source of electricity (not shown) vat the surface of the well. A perforating charge 19 for jet perforation of the casing is disposed in each" of the perforator ports. The construction and use of shaped charges are well known in the art. They comprise a charge which is rigidly enclosedpexcept at the location Ifrom which the jet is to issue.' This location is plugged by a metal retainer such as the conical retainer 15. These retainers form a cavity 19a in the charge, which usually is conical in shape, and which serves to cause the hot metal from the retainerand the hot gases from the perforating charge to issue in a jet from the enclosure holding the charge. As shownA in FIG. l, the jet will issue horizontally from the perfora tor ports 14, the retainers 15 being the weakest structural par-t of the enclosure. A

A lower central bore 20 is drilled upward through the carrier and intersects with four or more radially extending gas ports 21, the ends of which are closed by seals 21a.,

The lower central bore is closed off by a plug 22 Which is threaded into the bore at the bottom. The leads 17 extend through the low resistance detonator `18 and through the body 10 into the lower bore 20 where they are connected to a high resistance igniter 24l attached to a pro-` pellant charge 24a. The leads 17 `are preferably sealed t tion, has an annular groove 25 above the perforator ports- 14 and gas ports 2l. A retainer shoulder 26 projects from the carrier at the upper edge of this groove. A bathe ring 27, which can be a hollow O ring if desired, is placed within the groove so as to bear against both the carrier and the well casing. This 0 ring is flexible and unitary.

This creates a ilexible barrier or boundary between thev carrier and the casing, which will permit liquid to pass upwardly of the baille ring as the carrier is lowered. into position and enable the liquid to be'displaced upwardly when gas is discharged from the carrier below said bar.

lIt will be appreciated that a greater or lesser number of gas ports, and perforator ports can be used if desired, and also that other kinds of propellant or gas-generating charges can be used. The selection and number of these' elements will depend on the conditions under which the device is to be used.

FIG. 4 shows another type of perforating device according to the invention. A central tube 30 serves as a carrier andhas a closure plug and wire line socket 31 threaded into its upper end. A gas-producing charge 32, preferably of propellant material, is attached to this plug within the tube. This charge 32 can conveniently be compacted to a cylindrical shape. Electric lead Wires 33 from inside the line 45 pass to the propellant for setting oif the gas-producing charge. A lexible sleeve 35 of an impermeable material such as rubber is affixed to the opposite ends of the tube so as to surround the tube. Holes G4 in the walls of the central tube provide cornmunication between the inside of the tube 30 and the inside of the sleeve 35, so that the sleeve is adapted to be inated.

A pipe 36 connects with the bottom of the central tube 30. A lreceptacle 37 has a central passage 38 therethrough, and two or more perforator ports 39 which extend outward from the central passage 38. Shaped charges 39a are placed in these perforator ports, and are held therein by retainers 40 at their outer ends. Plugs 4tb act as inner retainers to hold the charges in the ports. A heat sensitive igniter itin is inserted into the end of each perforating charge and projects into the central passage 38. Another pipe 36a connects with the central passage 38 at one end, and with a gas distributor 41 at the other. The gas distributor has several `gas ports 42 which connect with the pipe 36a.

The carrier can be suspended in a well casing 43 by a line t5 attached to wire line socket 31, the `line being paid out from the surface of the well. The line 45` also carries electric leads 33.

FIG. illustrates still another form of the invention in which the perforating means are completely protected from well liquids at all times. A carrier 50 with a substantially circular cross-section throughout its length has an upper chamber 51, and a lower bore 52 connecting with the chamber. The upper chamber is closed by a wire line socket 53, and the lower` bore by la plug 54. 'A series of gas ports 55 and two or more perforator ports 56 are drilled through the carrier Wall from the lower bore.

A exible sleeve 57 made of impermeable material such as rubber surrounds the lcarrier and is bound to the carrier by straps 53 `at each end of the sleeve. Rubber reinforcing patches 5? are fixed to the inside of the sleeve opposite perforator ports.

A gas-producing charge 60, preferably of a propellant mixture, is placed in the upper chamber, and is connected by electric lead wires 61 to :a source of electricity (not shown). The charge 60 can conveniently be compressed to a cylindrical shape. Shaped perforating charges 62 having a cylindrical cross-section and a conical cavity 62a in their outer end are placed in the perforatirrg ponts with frangible retainers 63 at the carriers outer surface, and plugs 63a at the bore 52. Heat sensitive detonators 64 are inserted through plugs 63a into the propellant charges so as to project into the lower bore 52.

The carrier is suspended in -a well casing 65 fby a line 66 which is paid out from the surface. The line is attached to the wire line socket 53 on the carrier.

FG. 6 illustrates -another form of the invention in which a carrier 7b has an upper chamber 71 and a lower passage 72 which are separated by a frangible disc 73. The upper chamber is closed by a threaded wire line socket 74. A gas producing charge 75 is placed in the upper chamber and is connected by electric lead wires 76 enclosed inside la line `84. to a source of electricity (not shown). This charge 75 is conveniently compressed to a cylindrical shape.

Two perforating ports 77 are drilled to interconnect with the lower passage or gas port 72, and perforating means such as shaped charges 78 with retainers 79 are inserted therein. Heating-sensitive detonators 80 are inserted into the shaped charges so as to project into the lower passage 72.

A exible baffle S1 is held between two spaced annular shoulders 82 Welded or otherwise secured to the carrier, and projects from the cairier so as to bear against both the carrier and the Well casing 83. The carrier is suspended in the well c-asing by a line 84 attached to the it wire line socket 74 on the carrier, the line being paid out from the surface.

The operation of these embodiments will now be described. ln all the forms shown, the carrier is irst lowered into the Well casing so that the perforating means are opposite the places to be perforated. When the carrier of FIG. l is inserted in the well casing, the sealing ring 27 makes a resilient yContact with both the casing and the carrier. The outer diameter of the uncompressed ring should therefore be somewhat greater than the inner diameter' of the well casing. Then the ring will be cornpressed when the carrier is lowered into the well, and will form a battle or boundary which retards upward flow of gaseous fluid past it, while permitting liquid to be displaced upwardly past the ring.

When the carrier is 'in the desired position the propellant charge is ignited by closing the circuit through the n lead lines 17. Some of the body of gas generated by the ignition of the propellant material escapes into the casing through gas ports 21. and, being less dense `than the well liquids, rises until it encounters the baffle ring 2.7. As v the gas 'flows into the well, the liquids in the well are displaced. After sulicient gas has been introduced under the sealing ring, the liquids will have been replaced by gas to a level below the baffle ring 27 and below the perforator ponts 14. These ports are thus entirely surrounded by a gaseous medium.

The perforating means then be tired, in this case by sending lan electric current through leads 17 to ignite the squib 18 which detonates the shaped charge. rEhe jet blasts then discharge through the perforator ports, and the surrounding gaseous medium to perforate the casing.

When the device shown in FIG. 4 is lowered into the Well, a tight ft is not made with the casing at once, since the flexible sleeve 35 is uninfiated. Therefore when the carrier is positioned properly, an electric current will be sent through Ilead wire 33 to ignite the gas-producing charge 32. Gas thereupon ows through holes 34 to the inside of the flexible sleeve 35. This inflates the sleeve, creating an expansible chamber inside it, and making the necessary tight it with the well casing. This creates the fluid retarding barrier or boundary which extends between the carrier and the well casing.

Another portion of the generated gas ows through pipes 36 and 36a, and gas ports 42, to enter the well. This gas rises around the carrier lbeneath the barrier created by the inflated sleeve, and displaces the well liquids below the perforator ports 39.

T he igniters 40a are set oft" by the hot gases which ow around them and through the passage 38. The blast from the shaped charge then perforates the well casing, passing only through the gaseous medium provided by the envelope of gas around the carrier.

The device shown in FG. 5 operates in substantially the same manner as that of FIG. 4, except that the flexible sleeve surrounds both the gas ports 55 and the perforator ports 56. By this means, Well liquids are kept completely 'away lfrom the perforating charges. When the gas-producing charge is set olf, gases inflate the flexible sleeve 57 to produce an expansible chamber therein, `and expand that chamber so that the sleeve fits tightly against the casing. This action displaces liquids out of the region occupied `by the inflated sleeve. Hot gases also flow through lower bore 52 and contact the heatsensitive `detonators 80, thereby setting oif the perforating charges. The perforating charges then fire through the gas envelope and the sleeve itself. The sleeve must be replaced after each use.

The device shown in FIG. 6 is similar in operation to that of FIG. l, in that the gas producing charge is set oil? so as to flow directly into the well and displace liquids away from the exposed perforating ports. After an electric current ignites the gas-producing charge 75, and suiiicient pressure is generated, the frangible disc 73 breaks and releases Vthe gas from the chamber 71. The gas then ilows through lower passage 72 and -displaced'the well liquids beneath the barrier 81. The heat sensitive detonators 80 then ignite the perforator charges, which discharge through the gas envelope 'to puncture the casing. Y It will be noted that in the devices illustrated in FIGS. 1 through 6 the gas generated by the burning propellant is discharged from the carrier body in a generally horizontal direction. This is to avoid the creation of an upward thrust which would tend to force lthe carrier body up the well casing away tfrom the point at which the casing is to `be perforated. t

FIG. v7 illustrates an embodiment of the present invention wherein the gas `generated by the burning propellant is discharged from the carrier body in a ygenerally upward direction in order to create a downward thrust which not only holds the carrier body in xed position on the lower end of the supporting li-ne but also serves to increase the pull o n the suspension line, thereby indicating the -beginning and end of the gas generating cycle.

In FIG. 7 .the carrier body is indicated at 90 with a ilexible barrier 90a suspended within a well casing 91 from an electric line 9 secured in a socket 93 in the manner heretofore described. TheV carrier body 90 is chamber 95. A barrier wall 98 separates the propellant chamber 95 from the interior of the carrier body 90 to prevent the passage of hot gas from the propellant chamber into the interior of the carrier body. 'Ihe propellant chamber 95 is provided, near its upper end, with a series of upwardly directed discharge port-s 99 which are Vnormally closed by means of frangible seals 100.

The carrier body 90 contains air at atmospheric pressure which serves to cushion the shock caused by detonation of the shaped charges 101 contained therein. These shaped charges, and the associated detonatiug` cord 102, are of conventional design and form no part of the pres ent invention, being illustrative only. The jets from the t Y shaped charges pass through frangible seals 103 posij tioned in the wall of the carrier.

The leads from the electric line 92am connected to a detonator 104 for the explosive cord 102 and alsovto an igniter 105 in a propellant charge 106 within the propellant chamber 95. The leads 107 to the shaped charge 1 detonator may be of lower resistance than the leads 108 to the propellant igniter 105, or ya time delay relayV (not the shaped charge detonator and the propellant igniter, so that the propellant 106 can be ignited before the shaped charges lill-are detonated. This delay allows the gas generated by the propellant 106 to fully envelop the carrier body 90 before the shaped charges 101 are tired. A battle ring or barrier is employed to retard the upward movement of Ithe gases past the ports 103.

The gases issuing from the upwardly directed ports 99 will cause a downward thrust which will be imparted to and resisted by Ilthe electric line 92. The changes in thrust or weight on the line 92 are usually indicated by a weight indicator (not shown) at the top of the well associated with the line 92. A sudden increase in weight will indicate that the gas generator is in operation. After a predetermined elapsed time, sufficient to allow the car-` rier body 90 to become enveloped in gas, the shaped charge Yof the type described in connection with FIGS.

1-7. Materials of the thermit type (aluminum powder and i-ron oxide) :are well known as generators of heat with little or no gas being formed.

Since well perforators of the explosive type are almost always used below the surface of the uids which are in the well, a portion of such fluids (which are usually water, mud or oil) can be vaporized by the application of sufficient heat.

Apparatus for vaporizing a portion of the well uid, as shown in FIG. 8, is substantially similar to that shown in FIG. 7 except that the -propellant chamber 110 is provided wtih several open por-ts 111 which permit the well fluid to enter the interior of the chamber and surround the heat-generating charge 112. The latter is preferably enclosed in a iluid tight container 113, such as a steel shell or the like, which also encloses the igniter 114 on the end of the lead wires 115.

-In operatiomwhen the electric circuit through the lead wires 115 is closed, the igniter 114 will ignite the material 112 inside the shell 113. Heat of combustion of the material 112 will destroy the shell 11-3 and will vaporizeV a portion `of the Well fluid within the chamber 110. The vapors will issue through the ports 111 and form a gaseous envelope around the perforating tool, as previously described in connection with FIGS. 6 7.

Propellant materials such as are used as fuels in rocket propulsion are to be preferred as gas-producing materials. These propellant mixtures are selected and compounded for maximum heat and gas emission per uni-t of weight. They are also self-combustible in that they contain all substances necessary for the reaction, and do not depend on the atmosphere for the oxygen used in the reaction, nor do they requirev any other substances from other sources. They `are therefore excellent substances for creating the gas envelope. It will be appreciated, howcharges 101'are fired. The jets issuing from the shaped FIG. 8 illustrates an embodiment of the present ini vention wherein the gas envelope is generated by the yapplication of heat to a well iluid, rather than by the chemical reaction of the ingredients comprising a propellant ever, that substances which are not primarily suited for propellants can also be used, the only requirement being simply the ability to generate a body of gas.

zIn addition to its usefulness as a perforator, this device can .also be used as a pipe cutter by providing a large enough number of jet bla-sts -to make `a continuous perforation around 4the casing or pipe. It will also be appreciated that perforating means other than jet blasts may be used .as for example, bullet-type guns.

This invention provides a gas envelope for displacing Well liquids from the region through which a perforating means must pass, and retaining an envelope of gas around the perforating meausso that these means need pass only through gases. This increases the eiiiciency and penetration of the perfor-ating means.

My invention is not to be limited by the embodiments shown in the drawings and described in the description, which are given by way of example rather than of limitation, but only in accordance with the scope of the appended claims.

I claim:

l. The method of perforating a well comprising placing within the Well a carrier having a yielding barrier member adapted to pass uid from a region of'vhigher pressure to a region of lower pressure when in operative position and adapted to extendbetween the carrier and the wall of said well, and discharging a body of gas into the lwell below said barrier member whereby liquids are displaced past said barrier to form a gas-lled region immediately below said barrier member, and then firing perforating `means through said gas-filled region.

2. A well casing perforator comprising a carrier adapted to iit withinthe casing, a flexible sleeve attached to and surrounding the carrier, forming an expansible cham ber betweenthe sleeve and the carrier, propellant operated well casing perforating means disposed in the carrier below the sleeve and directed toward the casing, and means disposed in the carrier for releasing a body of gas into said sleeve to provide a resilient barrier between the carrier and the casing when in operative position comprising a charge of self-combustible propellant mate-v rial, the ignition of which produces the body of gas, means for discharging a portion of said body of gas into the casing below the barrier whereby liquids are displaced from the vicinity of the perforating means, and means providing a gas iiow passage from said discharge means to said gas releasing means and said perforating means.

3. The method of perforating a well containing fluid, by the use of a carrier provided with a yieldable barrier means adapted to extend between the carrier and the wall of the well containing perforating means comprising; p0- sitioning in said carrier materials which can react to generate heat within the carrier, submerging said carrier to a predetermined depth in the well, permitting a portion of the well iluid to enter the carrier and surround said heat generating materials, initiating generation of heat by reaction of said materials to Vaporize said well iluid by the heat generated, discharging said vapor outwardly of the carrier into the well opposite said perforating means, and subsequentl while said carrier is enveloped in a body of vapor, initiating said perforating means.

4. A propellant operated well casing perforator comprising, a carrier adapted to tit within a casing, a yieldable barrier arranged peripherally around said carrier and adapted to extend between the carrier and the casing, said barrier being adapted to pass fluid from a region of higher pressure to a region of lower pressure when in operative position, casing perforating means disposed in the carrier below the barrier and adapted to be directed toward the casing, and means arranged within said carrier for releasing a body of gas from said carrier below said barrier, whereby liquids within the casing in the vicinity of said perforating means are displaced.

5. Apparatus according to claim 4 in which the generated gas is discharged outwardly and upwardly to provide a downward'thrust on the carrier and cable on which said carrier is suspended and thus give an above ground indication of the operation of the device.

6. A propellant operated well casing perforator comprising, a carrier adapted to fit within a casing, gas body generating means disposed within said carrier a yieldable barrier arranged peripherally around said carrier and adapted to extend between the carrier and the casing, said barrier when in operative position being adapted to pass iiuid from a region of higher pressure to a region of lower pressure, propellant actuated casing perorating means disposed in the carrier below the barrier and adapted to be directed toward the casing, said perforating means being operative in response to ignition of the propellant contained therein, and means arranged within said carrier forgreleasing gas to said propellant actuated casing perforating means and from said carrier below said barrier, whereby liquids within the casing in the vicinity of said perforating means are displaced in said casing and said perforating means are activated in response to generation of said body of gas by said gas body generating means.

References Cited in the file of this patent UNITED STATES PATENTS 2,343,087 Schlumberger Feb. 29, 1944 2,558,924 Blake July 3, 1951 2,696,259 Greene Dec. 7, 1954 2,740,478 Greene Apr. 3, 1956 2,866,508 Church Dec. 30, 1958 

